Natural hybridization in mangroves: molecular approach to hybrid identification, maternity confirmation and introgression

Abstract

Interspecific natural hybridization is important in plant evolution. The occurrence of natural hybridization is not random, and varies in frequency among families and genera. Natural hybrids are only known in three genera of major mangrove families, recognized based on morphological criteria. Many morphological traits are subject to environmental influences, and to complications arising from character convergence and homoplasy, so neutral molecular markers should be used to verify natural hybridization, introgression and maternity. Natural hybridization in three major mangrove genera, Bruguiera, Rhizophora, and Sonneratia, was examined using ISSR, cpDNA and ITS sequences. All natural hybrids in these genera, resulting from interspecific hybridization between closely related taxa, were confirmed. The maternal species involved in the hybridization were identified. The suitability of ISSR markers was shown for detecting introgression in Bruguiera populations that occupy a wide geographical area. The evolutionary consequences of potential gene flow among sympatric species through introgressive hybridization are discussed.